The research proposed will deal with the following aspects of the analysis of malignancy in the mouse: 1. Fusion of cancer cell with haploid oocyte and diploid zygote; 2. Analysis of malignancy of resulting hybrids; 3. Ultrastructure of ovum activation resulting from fusion; 4. Adenyl-cyclase activity levels in initial hybrids, and tumor cells arising from these hybrids in vivo. BIBLIOGRAPHIC REFERENCES: P. Soupart and P.A. Strong. Ultrastructural Observations on Polyspermic Penetration of Zona Pellucida-free Human Oocytes Inseminated In Vitro. Fertil. Steril. 26 : 523-537, 1975. P. Soupart. Fecundacion Humana Experimental. Sexualmedica, #13, Febrero, 9-31 and 70-74, 1975.